Purification of organic compositions by sublimation

Abstract

A method purifies a starting solid or semi-solid organic composition located in a chamber. The method includes heating the starting organic composition such that molecules of one organic molecular species sublime out of the composition and molecules of a desired organic molecular species remain in the composition. The method includes pumping the chamber during the heating step to remove sublimed organic molecules. The method includes then, heating a remaining portion of the composition at one or more higher temperatures such that molecules of the desired organic molecular species sublime from the remaining portion of the composition. A separate region of the chamber is maintained under conditions that cause deposition of sublimed molecules of the desired species during the heating a remaining portion.

1 . A method for purifying a starting solid or semi-solid organic composition located in a chamber, comprising: 
 heating the starting solid or semi-solid organic composition such that molecules of one organic molecular species sublime out of the composition and molecules of a desired organic molecular species remain in the composition;    pumping the chamber during the heating to remove sublimed organic molecules; and    then, heating a remaining portion of the composition at one or more higher temperatures such that molecules of the desired organic molecular species sublime from the remaining portion of the composition, a separate region of the chamber being maintained under conditions that cause deposition of sublimed molecules of the desired organic molecular species therein during the heating a remaining portion.    
   
   
       2 . The method of  claim 1 , wherein the first heating step maintains the composition below a sublimation temperature of the desired organic molecular species and the second heating step causes the portion of the composition to have one or more temperatures greater than said sublimation temperature.  
   
   
       3 . The method of  claim 1 , further comprising maintaining a pressure of a background gas in the chamber during the second heating step.  
   
   
       4 . The method of  claim 3 , wherein the background gas is an inert gas.  
   
   
       5 . The method of  claim 2 , wherein the region is held below the sublimation temperature during the heating of a remaining portion.  
   
   
       6 . The method of  claim 1 , further comprising stopping the heating of a remaining portion of the composition prior to subliming the entire remaining portion.  
   
   
       7 . The method of  claim 1 , wherein the desired molecular species has a sublimation rate, the sublimation rate during the second heating step being at least two times higher than the sublimation rate during the first heating step.  
   
   
       8 . An apparatus, comprising: 
 a hermetically sealed, elongated, silicate glass ampoule; and    a pure sample of a single organic molecular species located in a hollow cavity in the ampoule; and    wherein the ampoule has glass bumps at opposite ends of the hollow cavity.    
   
   
       9 . The apparatus of  claim 8 , wherein the silicate glass is a borosilicate glass.  
   
   
       10 . The apparatus of  claim 8 , wherein the sample is a crystalline sample.  
   
   
       11 . The apparatus of  claim 8 , wherein the ampoule includes a partial pressure of a noble gas.  
   
   
       12 . The apparatus of  claim 8 , wherein the partial pressure between about 0.9 atmospheres and about 1.1 atmospheres.  
   
   
       13 . The apparatus of  claim 11 , wherein the gas is argon.  
   
   
       14 . The apparatus of  claim 11 , wherein the sample has a sublimation temperature.  
   
   
       15 . The apparatus of  claim 11 , wherein a sublimation rate of the sample below the sublimation temperature is at least 2 times smaller than the sublimation rate of the sample at a temperature above the sublimation temperature.  
   
   
       16 . A method for purifying a starting organic composition located in a chamber, comprising: 
 heating the starting organic composition at one or more first temperatures to sublime molecules from the composition, the one or more first temperatures being below a sublimation temperature of a desired organic molecular species;    pumping the chamber during the heating to remove subliming molecules; and    then, heating a remaining portion of the organic composition at one or more second temperatures to sublime the desired organic molecular species from the remaining portion of the organic composition, the one ore more second temperatures being equal to or greater than the sublimation temperature for the desired molecular species, a region of the chamber being maintained under conditions that enable crystallization of sublimed molecules of the desired organic molecular species during the second heating step.    
   
   
       17 . The method of  claim 16 , further comprising maintaining a pressure of an inert background gas in the chamber during the second heating step.  
   
   
       18 . The method of  claim 16 , wherein the region is held at a temperature lower than the sublimation temperature during the second heating step.  
   
   
       19 . The method of  claim 16 , further comprising stopping the heating of a remaining portion of the composition prior to the remaining portion disappearing.